A Saudi court on Monday overturned five death sentences over journalist Jamal Khashoggi’s murder in a final ruling that was condemned by his fiancée and slammed by a UN expert as a “parody of justice”.

Eight unnamed defendants were handed jail terms of between seven and 20 years in a verdict that comes after Khashoggi’s sons “pardoned” the killers in May, paving the way for a less severe punishment.

The court ruling underscores Saudi efforts to draw a line under the October 2018 murder as the kingdom seeks to reboot its international image ahead of November’s G20 summit in Riyadh.

“Five of the convicts were given 20 years in prison and another three were jailed for seven to 10 years,” the official Saudi Press Agency said, citing a spokesman for the public prosecutor.

None of the defendants were named in what was described as the final court ruling on the murder, which triggered an international outcry and tarnished the global reputation of Crown Prince Mohammed bin Salman.

Hatice Cengiz, the Turkish fiancée of the slain journalist, branded the verdict a “farce”.

“The ruling handed down today in Saudi Arabia again makes a complete mockery of justice,” Cengiz said on Twitter.

Agnes Callamard, the UN special rapporteur on extrajudicial, summary or arbitrary executions, slammed the ruling as “one more act today in this parody of justice”.

“These verdicts carry no legal or moral legitimacy,” Callamard wrote on Twitter. “They came at the end of a process which was neither fair, nor just, or transparent.”

Khashoggi – a royal family insider turned critic – was killed and dismembered at the kingdom’s consulate in Istanbul in October 2018, in a case that tarnished the reputation of the de facto ruler Prince Mohammed.

A critic of the crown prince, the 59-year-old Khashoggi was strangled and his body cut into pieces by a 15-man Saudi squad inside the consulate, according to Turkish officials. His remains have not been found.

Riyadh has described the murder as a “rogue” operation, but both the CIA and a United Nations special envoy have directly linked Prince Mohammed to the killing, a charge the kingdom vehemently denies.

Callamard also criticised the fact that “high-level officials” behind the murder have “walked free from the start”, and that Prince Mohammed has remained protected against “any kind of meaningful scrutiny”.

In December, a Saudi court exonerated two of the crown prince’s top aides over the murder – deputy intelligence chief Ahmed al-Assiri and the royal court’s media tsar Saud al-Qahtani.

Both aides were part of Prince Mohammed’s tight-knit inner circle and were formally sacked over the killing.

“Since the beginning, there was never any intent to hold those responsible to account, only repeated attempts to cover it up,” said Ines Osman, director of the Geneva-based MENA Rights Group.

“This verdict is the last nail in the coffin, saying ‘the case is now closed’.”

The closed-door trial of 11 suspects ended in December with five unnamed people sentenced to death and three others handed jail terms totalling 24 years over the killing. But the family’s pardon paved the way for Monday’s reduced sentences, including granting clemency for the five people on death row.

The Washington Post reported last year that Khashoggi’s children, including his son Salah, had received multimillion-dollar homes and were being paid thousands of dollars per month by authorities. Salah rejected the report, denying discussing a financial settlement with Saudi Arabia’s authoritarian rulers.

In July, 20 Saudi suspects including Assiri and Qahtani went on trial in absentia in Turkey.

The former top aides were formally charged in March with “instigating the deliberate and monstrous killing, causing torment”.